We will use enriched myeloid stem cell (CFU-C) populations from human bone marrow with highly purified colony-stimulating factor (CSF) to study myeloid cell differentiation in vitro. This CSF and others will be used to grow leukemic stem cells in culture. Our studies will characterize the effects of several growth (differentiation) enhancing agents such as hemin and beta-mercaptoethanol on normal and leukemic stem cells in culture. We will develop methods to screen bone marrow cultures by using specific monoclonal antibodies against normal marrow antigens to accurately identify colony phenotypes. We will screen monoclones against leukemic blasts for specificity with normal and leukemic cell suspensions by using a fluorescence activated flow cytometer.